The present invention relates to a sealed battery and a method of manufacturing the same and, more particularly, to a sealed battery having an improved structure for sealing an electrolyte injection hole, and a method of manufacturing the same.
Conventional sealed batteries of this type, e.g., prismatic sealed batteries, have the following structures:
(1) a sealed battery including a metal outer jacket having a prismatic shape with a bottom, an electric-power generating element housed in the outer jacket, an electrolyte injected through the electrolyte injection hole, and a metal lid welded to the opening portion of the upper end of the outer jacket and having an electrode terminal insulated by a hermetic seal; PA1 (2) a sealed battery including a metal outer jacket having a prismatic shape with a bottom, an electric-power generating element housed in the outer jacket, an electrolyte injected through the opening portion of the outer jacket, and a metal lid joined to the opening portion of the upper end of the outer jacket by clamping and having an electrode terminal insulated by a hermetic seal; and PA1 (3) a sealed battery including a metal outer jacket having a prismatic shape with a bottom, an electric-power generating element housed in the outer jacket, a lid made of a metal plate material, welded to the opening portion of the outer jacket and having an electrode terminal insulated by a hermetic seal and an electrolyte injection hole, the electrolyte injected into the outer jacket through the electrolyte injection hole in the lid, and a spherical or hook-like plug member inserted into the electrolyte injection hole and joined by brazing or resistance welding. PA1 a battery case having a structure in which a metal lid is welded to an opening portion of a metal outer jacket; PA1 an electric-power generating element housed in the battery case and having a positive electrode and a negative electrode with a separator being sandwiched therebetween; PA1 an injection hole formed in the battery case to allow an electrolyte to be injected; and PA1 a sealing lid made of a metal plate material which is seam-welded to the battery case including the injection hole by a laser beam, PA1 wherein the sealing lid has a weld portion formed by the laser beam to have a closed loop surrounding the injection hole to be seam-welded to the battery case, and at least one of start and end points of the weld portion is located outside the closed loop. PA1 assembling a battery case by welding a metal lid to an opening portion of a metal outer jacket; PA1 housing an electric-power generating element in the battery case and the element having a positive electrode and a negative electrode with a separator being sandwiched therebetween; PA1 forming an injection hole in the battery case and injecting an electrolyte into the case through the injection hole; and PA1 placing a sealing lid made of a metal plate material on an outer surface of the battery case including the injection hole, and seam-welding the sealing lid to the battery case to seal the injection hole, PA1 wherein the seam-welding process is performed by forming a weld portion on the sealing lid by a laser beam such that the weld portion has a closed loop surrounding the injection hole and at least one of start and end points of the weld portion is located outside the closed loop.
According to the prismatic sealed battery having the structure (1), the lid is welded to the opening portion of the upper end of the outer jacket in an atmosphere in which the electrolyte stored in the outer jacket is evaporated. The electrolyte vapor condensed in the welding area between the outer jacket and the lid causes weld defects, resulting in a considerable deterioration in sealing properties.
According to the prismatic sealed battery having the structure (2), since the outer jacket, to which the lid is joined by clamping, has a prismatic shape with a bottom, the process conditions of clamping corner portions are different from that of clamping side portions resulting in a severe deterioration in sealing properties.
According to the prismatic sealed battery having the structure (3), the plug member is inserted into the electrolyte injection hole, and is joined by resistance welding or brazing. The plug member may undergo joining failure due to evaporation of the electrolyte. In addition, when the lid is to be formed by using aluminum to reduce the weight, it is difficult to join the plug member in the electrolyte injection hole of the lid by brazing or resistance welding.
Note that a sealed battery having an electrolyte injection hole formed in the bottom or side surface of an outer jacket also has the same problem as that posed in the batteries having the liquid injection holes in the lids because they have the same structure except for the positions of the electrolyte injection holes.
In cylindrical sealed batteries as well as prismatic sealed batteries, with the technique (1), weld defects degrade sealing properties for the same reason as that for the prismatic sealed batteries. According to the technique (2), in the case of a cylindrical sealed battery, since clamping conditions are uniform, better sealing properties can be obtained than in the case of a prismatic sealed battery. In comparison with a battery using welding, the sealing properties of this battery deteriorate during operation, especially in a high-temperature environment. With the technique (3), joining failure occurs or joining itself is difficult to perform for the same reason as that for prismatic sealed batteries.